Nominal size: 16 1/2x21 1/2x1; Actual size: 16 1/2"x21 1/2"x3/4"; This MERV 8 filter is comparable with MPR 600 & FPR 5. Designed to filter microscopic particles such as lint, dust mites, spores, and pollen Simple to install and a cost-effective step towards a healthier home environment. For best results, change your filters every 60 to 90 days but increase frequency to 30 days during peak summer and winter months 100% synthetic electrostatic media for high efficiency with low air flow resistance Manufactured by Filtration Group, a world-leading manufacturer and supplier of filtration solutions making the world safer, healthier & more productive.